JP6359542B2 - Method and apparatus for inspecting subscriber premises equipment - Google Patents

Description

  The present invention relates to a method for inspecting customer premises equipment comprising a digital subscriber line (DSL) modem coupled to a telecommunications line. The invention further relates to each computer program product such as a storage medium containing such a device for inspecting customer premises equipment, each monitoring station and a computer program for carrying out such a method.

  Communications subscriber lines are not only traditional narrowband services such as conventional regular telephone service (POTS) or integrated services digital network (ISDN) access, but also broadband services such as Internet access or Internet Protocol Television (IPTV). Often used to access Broadband access is commonly referred to as digital subscriber line (DSL). In order to operate a conventional narrowband service and DSL service simultaneously on the same subscriber line, these two types of services use different frequency ranges on the communication line. The low frequency range is used for narrowband services such as POTS or ISDN, and the higher frequency range is used for DSL.

  Accordingly, customer premises equipment (CPE) typically comprises a splitter for connecting both narrowband and broadband service terminal equipment or network termination equipment to a single communication line. The splitter comprises a low pass filter configured to prevent high frequency DSL signals from propagating to terminals or network termination equipment used for conventional narrowband services. The low pass filter protects the DSL signal from high frequency disturbances that may be caused by terminals for narrowband services and network termination equipment, particularly analog telephones. Furthermore, the low-pass filter prevents DSL signals from propagating to terminals for narrowband services or network termination equipment, particularly analog telephones, thereby avoiding audible noise, for example during telephone communications.

  It is possible for a customer to mistakenly connect a DSL device, in particular a DSL modem, to a connector on a splitter that is intended to be connected to a narrowband terminal or network termination equipment (eg analog telephone or ISDN network termination). If the narrowband service is POTS, the telephone is connected to the splitter connector that is intended to be connected to the DSL modem (modem connector), and the DSL modem is connected to the splitter connector that is intended to be connected to the telephone. There is a risk of being connected. If CPE components are interconnected in error, DSL signals that are completely within the stop band of the splitter's low pass filter may be greatly attenuated while approaching the DSL modem. As a result, the performance of the DSL service is significantly degraded, and in many cases the DSL modem may not even be synchronized with the network operator's access node (eg, DSL access multiplexer, DSLAM).

  Known to inspect communication lines between network operators and subscribers, such as Metal Line Testing (MELT) or Single Ended Line Test (SELT), which are generally involved in troubleshooting DSL connections Some inspection methods may not reveal physical defects in the communication line. Therefore, costly and time consuming investigations are often required to identify problems.

  Accordingly, it is an object of the present invention to provide an apparatus and method that enables detection of incorrectly connected splitters without the need for manual intervention from a service provider.

  According to one embodiment, a method is provided for inspecting a customer premises equipment comprising a DSL modem coupled to a communication line of a communication network, the method being transmitted to a DSL modem over a communication line, or Determining at least one value depending on the attenuation of a signal received from a DSL modem over a communication line, and a modem connector for which the DSL modem is intended to be connected to a DSL modem. Responsive to the value detecting that the DSL modem is coupled to the communication line via the DSL splitter in a manner that is connected to a different connector of the DSL splitter. The interconnection of parts of the customer premises equipment in which the DSL modem is connected to the different connector, i.e. to the wrong connector, is also referred to as a "wrongly connected splitter" or "reverse splitter". By considering the values that characterize the attenuation, incorrect interconnections between the DSL modem and the DSL splitter can be detected fairly deterministically. This is because the low pass filter of the splitter causes much greater attenuation when the modem is connected to a different connector than the modem connector compared to when the modem is connected to the modem connector.

  In one embodiment, the method includes determining a loop length value that depends on a loop length of the communication line, wherein the detecting step depends on the determined loop length value. The step of detecting the loop length dependence increases the reliability of the method. The loop length is the length of the communication line. In one embodiment, the loop value may thus correspond to a length unit, eg, a length expressed in meters. In another embodiment, the loop length value may be expressed, for example, as a target loop length, ie, a line attenuation dependent loop length. The loop length value may be determined, for example, by a SELT measurement on the line, or by querying a database containing data about the loop length, for example, of a network operator.

  In one embodiment, the method includes determining a threshold as a function of loop length, and the detecting step is based on comparing the threshold to a value. In one embodiment, the threshold value may be predefined or may be obtained by manual user input. In another embodiment, the threshold is calculated by simulating the line. Preferably, the line simulation may cover a simulation scenario where the modem is connected to a modem port and a different simulation scenario where the modem is connected to a different port of the splitter other than the modem port.

  In one embodiment, the method concludes that the DSL modem is correctly connected to a line, eg, a modem connector, or is connected directly to the customer end of the communication line, the DSL modem being connected to the DSL modem. Conclude that it is connected to another connector and / or conclude that a definitive determination is not possible as to whether the DSL modem is connected to the modem connector or to another connector. including. Yet another connector may be any connector on a splitter that is different from a modem connector, eg, a connector for POTS terminals or ISDN terminal equipment such as telephones, fax machines, narrowband modems.

  Preferably, the concluding step relies on comparing the value with a first threshold and a second threshold. By comparing the value with two thresholds, cases where a definitive conclusion is not possible can easily be identified.

  According to one embodiment, the value corresponds to the loop attenuation of the communication line. In this embodiment, each threshold may be a loop attenuation threshold that can be compared to a measured loop attenuation value. Loop attenuation values and corresponding thresholds may be determined for signals transmitted to the modem over the communication line (downstream signal) and / or signals received from the modem over the communication line (upstream signal). Determining values for both downstream and upstream signals will increase the reliability of the method.

  In another embodiment, the value corresponds to the received signal power of a signal that includes at least one activation tone sent by the DSL modem over the communication line. In one embodiment, the received signal power is the signal power at the network end of the communication line, which is opposite the customer end of the line to which the modem is connected. In this embodiment, the received signal power can be measured by an access node (eg, DSLAM) connected to the network side end of the communication line. The received signal power decreases as the attenuation increases. Therefore, the received signal power is a value that depends on attenuation. Preferably, the received signal power corresponds to the signal power of a signal comprising at least one activation tone received, for example by an access node, at the end of the communication line opposite to the end of the line to which the modem is connected.

  In one embodiment, the method includes determining values for at least two different frequencies of the signal, preferably the frequencies of the two subsequent activation tones, and detecting the reverse splitter includes at least two different frequencies. May depend on the value corresponding to.

  In one embodiment, the method checks whether the rate at which the signal power decreases with the frequency of the signal is greater than a predefined rate threshold, and the step of checking is greater than the rate threshold. Concludes that the DSL modem is connected to a further connector. In an exemplary embodiment, the difference in measured signal power of two subsequent activation tones is not possible to determine whether the splitter is properly connected or based on the signal power difference. Can be calculated and compared to one or two signal power difference thresholds to conclude. In this exemplary embodiment, the speed threshold corresponds to at least one power difference threshold. The greater the speed, the greater the difference in measured signal power between the two subsequent activation tones.

  In one embodiment, the method checks whether the signal power increases with the frequency of the signal, and if the checking indicates that the signal power increases with the frequency, the signal is from another communication line. And a step of concluding that it is a result of crosstalk.

  In a preferred embodiment, the method includes determining whether the DSL modem is synchronized with an access node, preferably a DSLAM, and concludes whether the DSL modem is connected to the modem connector of the DSL splitter: If the modem is not synchronized, based on the signal power of the activation tone, the conclusion step is based on loop attenuation if the modem is synchronized. In other words, the at least one value may be signal power or loop attenuation. Preferably, either signal power or loop attenuation is used as the attenuation dependent value, depending on whether the modem and access node are synchronized with each other.

  According to another embodiment, an apparatus for inspecting customer premises equipment is provided, wherein the subscriber premises equipment comprises a DSL modem coupled to a communication line of a communication network, and the apparatus is connected to the DSL modem via the communication line. Determining at least one value depending on the attenuation of the signal transmitted or received from the DSL modem over the communication line, and the DSL modem is intended to be connected to the DSL modem of the DSL splitter Detecting, depending on the value, that the DSL modem is coupled to the communication line via the DSL splitter in a manner different from the modem connector being connected to the connector of the DSL splitter. It is possible to operate.

  In one embodiment, the device is preferably programmed and configured to perform the method according to the invention, the embodiment of which is described herein. The apparatus may comprise a control device or a computer whose embodiments are programmed to carry out the method according to the invention described herein.

  According to yet another embodiment, a monitoring node is provided that includes a communication interface (eg, a wireline interface such as an Ethernet interface or a wireless interface) for connecting the monitoring node to a network that includes subscriber premises equipment. The subscriber premises equipment comprises a DSL modem and the monitoring node comprises the above-described device for inspecting the subscriber premises equipment. In one embodiment, the monitoring node may include a computer, such as a desktop computer or server computer that corresponds to a personal computer (PC) architecture, which may include a communication interface, such as an Ethernet interface.

  According to yet another embodiment, a computer program product, preferably a computer readable storage medium comprising a computer program, is provided, which is programmed to perform the method according to the invention when running on a computer. And method embodiments are described herein. The storage medium may include a magnetic storage device (eg, a magnetic disk or tape), an optical storage medium (eg, an optical disk), or a semiconductor storage medium (eg, RAM, ROM, or flash memory).

  Exemplary embodiments and further advantages of the present invention are shown in the drawings and described in detail below.

It is a figure which shows a communication network. FIG. 2 is a schematic diagram showing a splitter of the network shown in FIG. 1. It is a figure which shows the transfer function of the low-pass filter of the splitter shown by FIG. It is a flowchart which shows the method of test | inspecting the subscriber premises equipment shown by FIG. It is a figure which shows the detail of the flowchart of FIG. FIG. 2 is a diagram showing loop attenuation upstream and downstream of the communication line of the network shown in FIG. 1 for different cable types and different loop lengths ranging from 0 m to 5000 m. FIG. 2 is a diagram showing loop attenuation upstream and downstream of the communication line of the network shown in FIG. 1 for different cable types and different loop lengths ranging from 0 m to 5000 m. It is a figure which shows the downstream attenuation | damping curve of the communication line of a different cable type and a threshold value. FIG. 9 is a view similar to FIG. 8 where the threshold depends on the length of the communication line. It is a figure which further shows the detail of the flowchart of FIG. With respect to the received signal power of different activation tones transmitted by the network's DSL modem in different situations, direct transmission from the DSL modem by a correctly installed splitter, direct transmission by a splitter that is not correctly connected, and proximity It is a figure which shows the transmission via the crosstalk from a communication line, and a threshold value. FIG. 12 is a diagram illustrating FIG. 11 in which a threshold value depends on a communication line length.

  The description and drawings merely illustrate the principles of the invention. Accordingly, although not explicitly described or illustrated herein, it will be appreciated that those skilled in the art will be able to devise various arrangements that embody the principles of the invention and fall within its spirit and scope. . Further, all examples given herein are primarily for instructional purposes to assist the reader in understanding the principles of the invention and the concepts that the inventors have contributed to the development of the art. It is expressly intended and should be construed as not being limited to such specific examples and conditions. Furthermore, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to include equivalents thereof.

  FIG. 1 shows a communication network 11 including a communication line 13. The communication line 13 has a pair 15 of conductors 15a and 15b, and a first end 16 of the pair 15 is connected to a network-side termination node of the network 11, which is further called an access node 17 and The second end 18 is connected to the terminal-side terminal node 19 of the network 11. The terminal-side terminal node 19 may be a part of the customer premises equipment (CPE 21) of the network 11.

  In the illustrated embodiment, the communication line 13 is a digital subscriber line (DSL) such as ADSL or VDSL. Thus, the access node 17 may be a DSL access multiplexer (DSLAM) or another type of DSL access node. The terminal end node 19 is a DSL modem or may include a DSL modem. However, the present invention is not limited to DSL. In another embodiment, the network 11 includes different types of communication lines 13.

  The access node 17 has a first modem circuit 23 to which the first end 16 of the pair 15 is connected via a network side splitter 24. In addition, the access node 17 has a first controller 25 configured to control the operation of the access node 17. In one embodiment, the first controller 25 is a programmable computer comprising a processor 27, such as a microprocessor, and a storage element 29, such as a semiconductor memory. Further, the network 11 may include network elements for conventional narrowband services such as a telephone network switch 30. The telephone network switch 30 may include an interface circuit configuration (eg, a line card) configured to connect to a POTS terminal (eg, analog phone or fax) or to an ISDN network termination device. The interface circuit configuration of the telephone network switch 30 is connected to the network side splitter 24. Thus, both the first modem circuit 23 and the network element 30 are coupled to the communication line 13.

  The terminal-side termination node 19 includes a second modem circuit 33 to which the second end 18 of the pair 15 is connected via the splitter 34 of the CPE 21. The splitter 34 is also called “POTS splitter” or “DSL splitter”. A customer-side narrowband terminal or narrowband network termination device 40 of the CPE 21 is also connected to the splitter 34. The narrowband terminal or network termination device 40 may comprise an ISDN network termination device such as a telephone or fax machine or a POTS terminal. Accordingly, the second modem circuit 33 and the narrowband terminal or network termination device 40 are coupled to the communication line 13.

  Further, the terminal-side terminal node 19 includes a second control device 31. The second control device 31 may have the same basic configuration as the first control device 25. That is, the second control device 31 is a programmable computer and may include the processor 27 and / or the storage element 29.

  In the illustrated embodiment, at least part of the pair 15 is part of the binder 35 and extends in parallel to at least one further communication line 36. Each additional line 36 includes yet another conductor pair 37. The binder 35 may include a shield 38 that is conductive, preferably metallic, and may be grounded as depicted in FIG.

  Furthermore, the network 11 may include an optional monitoring station 39, which is connected to at least one of the nodes 17, 19 via, for example, an interconnection network 41, and at least one of the nodes 17, 19; Preferably, it can communicate with the access node 17. Station 39 includes a third controller 43. The third control device 43 may have the same basic configuration as the first control device 25. That is, the third control device 43 is a programmable computer and may include the processor 27 and / or the storage element 29. In an exemplary embodiment, the station 39 may be a server, personal computer, PDA or handheld computer such as a mobile phone.

  At least one of the controllers 25, 31, or 43 is configured to perform a method for inspecting customer premises equipment comprising a terminal end node 19 such as a splitter 34 and a DSL modem. For this purpose, a computer program programmed to execute the method when at least one of the control devices 25, 31, 43 is operated may be provided. In other words, the method may be performed at the access node 17, the station 39, or the terminal end node 19. The computer program may be stored in at least one storage element 29. Further, the computer program may be stored in any type of data storage medium such as a magnetic disk or an optical disk or a semiconductor storage medium. Furthermore, the program can be provided by a server in transmission over a network, preferably the Internet.

  FIG. 2 shows the splitter 34 in more detail. The splitter 34 directly connects the communication line 13 to the terminal-side terminal node 19 through the modem connector 49. In the illustrated embodiment, the terminal end node 19 is a DSL modem. Therefore, for the sake of simplicity, the terminal end node 19 is further referred to as a “modem 19”. The splitter 34 includes a secondary LC low-pass filter 51 including an inductor L and a capacitor C. The low-pass filter 51 is disposed between the communication line 13 and the narrowband terminal or the narrowband network termination device 40. The narrowband terminal or network termination device 40 is connected to the low pass filter 51 by another connector 52. In the illustrated embodiment, the modem connector 49 and / or the further connector 52 are operable by a user of the CPE 21, for example, a network operator customer of the network 11. It may happen that the customer connects the modem 19 to a different connector instead of the modem connector 49, thereby causing the splitter 34 to be incorrectly connected. This incorrect connection of splitter 34 to modem 19 is further referred to as a “reverse splitter”. Typically, the customer not only connects the modem 49 to the incorrect connector 52, but also connects a narrowband terminal or network terminator 40 to the modem connector 49. Accordingly, the “reverse splitter” connection includes a case in which the two connectors 49 and 52 are connected to each other. In the case of the reverse splitter, the modem 19 is coupled to the communication line 13 via the filter 51 of the splitter 34. That is, the filter 51 is disposed between the customer-side end 18 of the communication line 13 and the modem 19. If not, i.e. if the splitter is correctly connected or if the CPE 21 does not have a splitter, the modem 19 is different from the communication line 13 (as shown in FIG. 2) or from the filter 51. They are coupled by a coupling circuit configuration (not shown).

  FIG. 3 shows the transfer function 53 of the low-pass filter 51. In the diagram shown in FIG. 3, the frequencies of three activated tones (tone 9, tone 17 and tone 25) are shown. The activation tone is transmitted by the second modem circuit 33 after the modem 19 is turned on and before the DSL modem 19 synchronizes with the access node 17. These activation tone frequencies are labeled 55a, 55b and 55c, respectively. The transmission of activation tones 55a, 55b, 55c is part of the handshake procedure performed in the first stage of the initialization of the DSL connection between the first modem circuit 23 and the second modem circuit 33. The second modem circuit 33 typically transmits these activation tones 55a, 55b, 55c and waits for a response transmitted by the first modem circuit 23 of the access node 17. In ADSL and ADSL 2/2 +, the activation tone has a pre-defined frequency as defined in ITU-T recommendation G994.1. They correspond to tones 9, 17 and 25, respectively. The entire DSL spectrum is divided into a number of tones, each associated with a subcarrier at a frequency corresponding to the tone index multiplied by 4.3125 kHz. Thus, in ADSLx, the activation tone has frequencies of 38.3125 kHz, 73.3135 kHz, and 107.8125 kHz, respectively. In FIG. 3, tone 9 is assigned 55a, tone 17 is assigned 55b, and tone 25 is assigned 55c.

  FIG. 4 shows an overview of the method 57 for checking the CPE 21 for the presence of the reverse splitter 34. After the start 59 of the method 57, the branch 61 of the method 57 checks whether the modem 19 is synchronized with the access node 17. If branch 61 concludes that modem 19 and access node 17 are synchronized with each other (Y), method block 63 is executed. Block 63 depends on whether the modem 19 is connected to the modem connector 49 or is connected to a different connector of the splitter 34, such as another connector 52, depending on the loop attenuation of the communication line 13, i.e. the splitter 34. Determine if is reversed. Details of block 63 are shown in FIG. 5 and described below.

  If step 61 concludes that modem 19 and access node 19 are not synchronized with each other (N), a further block 65 of method 57 is executed. Block 65 determines whether the splitter 34 is reversed in response to the signal power of the at least one activation tone 55a, 55b, 55c sent by the DSL modem 19. Block 65 is shown in detail in FIG. 10 and is described below. After block 63 or block 65 is complete, method 57 ends at step 67.

  In the illustrated embodiment, the method 57 automatically determines in step 61 whether block 63 or block 65 must be executed. In another embodiment, method 57 does not include branch 61 and the determination of whether to execute block 63 or block 65 needs to be performed manually. In another embodiment, method 57 includes block 63 but does not include branch 61 and block 65. In yet another embodiment, method 57 includes block 65 but does not include branch 61 and block 63. In the latter two embodiments, the method 57 may check the subscriber premises equipment 21 respectively based on loop attenuation alone or based on signal power of at least one activation tone 55a, 55b, 55c only. it can.

If the modem 19 is synchronized with the access node 17 but is connected to the wrong connector 52 of the splitter 34, this incorrect connection will cause the downstream loop attenuation A _DS of the communication line 13 and / or the upstream loop of the line 13. Can be detected in response to attenuation A _US . This loop attenuation A _DS , A _US may be measured continuously by two modem circuits 23, 33 in the access node 17 or modem 19, respectively. Loop attenuation A _DS , A _US corresponds to the average signal attenuation observed in the downstream and upstream bands, respectively. Since the entire spectrum used for DSL transmission between the modem circuits 23, 33 is within the stop band of the low pass filter 51 of the splitter 34, the modem 19 is a different connector than the modem connector 41, in particular a further connector 52. The DSL signal will be greatly attenuated by the splitter 34. As a result, the loop attenuation is much higher than would be observed when the splitter 34 is correctly connected.

6 and 7, the upstream (US) loop attenuation A _US is plotted against the downstream (DS) loop attenuation A _DS for a loop length, ie, the length of the communication line 13 in the range of 0 to 5000 meters. Yes. Circles show plots for the case where the splitter 34 is correctly connected (left plots in FIGS. 6 and 7). The diamond-shaped plots on the right of FIGS. 6 and 7 refer to the case where the splitter 34 is reversed. In FIG. 6, the attenuation is plotted for a 24 AWG cable. FIG. 7 shows the same plot as FIG. However, in FIG. 7, a 26 AWG cable is considered.

  In the scenario shown in FIG. 6, by comparing the signal attenuation value to a threshold value, the case where the splitter 34 is correctly connected to the modem 19 or not can be detected. However, in the scenario shown in FIG. 7, this determination may not be performed deterministically. This is because the normal attenuation observed in the long loop 13 with the splitter 34 properly connected can be greater than the attenuation observed in the short loop 13 where the splitter 34 is not correctly installed. . This uncertainty can be eliminated by considering not only the loop attenuation but also the estimated loop length, as described in detail below.

  As shown in FIG. 5, block 63 includes a step 69 of simulating downstream and upstream loop attenuation for all possible cable types in the possible loop length range. In one embodiment, the possible cable types and possible loop length ranges include all cable types and loop length ranges that may exist in any network 11. In another embodiment, the possible cable type and loop length ranges are limited to cable types and loop lengths that exist in a certain operator's network 11 or are used in a certain geographic region. Cable types include, for example, cable gauges, expressed as values in the American Wire Gauge Standard (AWG). For example, the cable may be a 24 AWG cable or a 26 AWG cable. The loop length may start at least approximately 0 and end with the longest loop length that may be several thousand meters, for example 5000 m. In the simulation at step 69, a mathematical cable model may be applied. The cable model parameters may include cable type parameters such as cable length and cable gauge. In one embodiment, the cable model may be a standard transmission line model. Standard cable model parameters (eg, distributed resistance R ', distributed inductance L', distributed capacitance C 'or distributed conductance G') may be set according to the characteristics of the cable, such as a cable gauge. The simulation results of step 69 may include the attenuation of a cable of a certain type and a certain loop length.

Step 71 of block 63 collects downstream loop attenuation A _DS and / or upstream loop attenuation A _US from modem 19 and / or access node 17. In particular, if method 57 is performed at monitoring station 39, a suitable communication protocol such as SNMP may be used to retrieve attenuation values A _DS , A _US from access node 17 or modem 19.

After the simulation results of step 69 become available and step 71 collects the attenuation values A _DS , A _US , branch 73 checks whether information regarding the loop length is available or can be generated.

If the loop length information is not available and cannot be generated (N), step 75 of block 63 is performed to calculate two thresholds, further called the normal threshold TN and the inverse threshold TR. Preferably, these threshold values are calculated separately for the downstream (DS) and upstream (US) directions, resulting in four threshold values TN _DS , TR _DS , TN _US , TR _US .

  Step 77 then determines whether the splitter 34 is reversed or whether a reliable determination of whether the splitter 34 is reversed is impossible.

FIG. 8 shows a method of calculating the two threshold values TN _DS and TR _DS in the downstream direction according to the simulation result calculated in step 69. Units depends on the loop length l of m, the unit is in the form of a downstream loop attenuation A _DS of dB, the simulation results are shown. In the example shown in FIG. 8, two possible cable types and a loop length range of 0 to 5000 meters are considered. The two solid lines show the downstream loop attenuation A _DS for two different cable types when the splitter 34 is correctly connected. The dashed and dotted lines show the downstream attenuation for the reverse splitter 34, which is when the modem 19 is connected to a further connector 52 of the splitter. In one embodiment, the normal threshold TN _DS is the case for the simulated downstream attenuation A _{DS for} all possible cable types, and generally for the reverse splitter (minimum of all dotted and dashed lines in FIG. 8). Calculated as the minimum of the possible loop length range.

The reverse threshold TR _DS can generally be calculated as the maximum of the downstream attenuation A _DS for all possible cable types in the possible loop length range (maximum of all solid lines in FIG. 8). . In the example shown, the normal threshold so obtained is about TN _DS = 70 dB and the reverse threshold is about TR _DS = 80 dB.

Considering the downstream attenuation A _DS measured for a particular line 13, in one embodiment, if the measured attenuation A _DS is less than the normal threshold required for the downstream direction, block if A _DS <TN _DS. 63 can conclude that the splitter 34 is correctly installed. If A _DS > TR _DS , where the measured attenuation A _DS is greater than the inverse threshold determined for the downstream direction, block 63 can conclude that the inverse splitter 34 is present. If the measured value is between these thresholds TN _DS and TR _DS , it is impossible to conclude deterministically and the method can conclude that it cannot determine whether the reverse splitter is present. .

FIG. 8 shows the calculation of the threshold values TN _DS and TR _DS for the downstream direction. However, these thresholds can also be calculated in the upstream direction by analyzing the corresponding upstream simulation. The obtained threshold values are called TN _US and TR _US . In one embodiment, block 63 compares the measured upstream attenuation value A _US with the two thresholds TN _US and TR _US in the manner described above for the downstream direction.

The embodiment shown in FIG. 5 is a threshold of corresponding values determined by analyzing the signal attenuation values A _DS , A _US measured both downstream and upstream and the simulation results as described above with respect to FIG. TN _DS , TR _DS , TN _US , TR _US are used. In particular, branch 79 in step 77 determines whether at least one attenuation A _DS , A _US is greater than the respective inverse threshold values TR _DS , TR _US , and the attenuation values A _DS , A _US are the respective normal threshold values. Check if it is below TN _DS or TN _US . If branch 79 concludes that this condition is satisfied (Y), step 81 of block 63 is performed to determine that the reverse splitter 34 has been detected for the particular communication line 13. After step 81, block 63 is terminated.

If the condition of branch 79 is not true (N), a further branch 83 is executed at step 77. The branch 83 is at least one measured attenuation value A _DS , A _US below the corresponding normal threshold TN _DS , TN _DS and the measured attenuation A _DS , A _US corresponds to the opposite threshold TR _DS , TR Check if it does not exceed _US . If so (Y), block 63 indicates that a correctly connected splitter 34 has been detected for a particular communication line 13 or that the modem 19 is connected directly to the line 13 without using a splitter. Step 85 is performed to determine whether or not there is. If not (N), step 87 is performed to determine that a definitive conclusion is not possible as to whether the splitter 34 is properly connected or vice versa. Block 63 ends after step 81, 85 or step 87.

Block 77 makes it possible to conclude whether the splitter 34 is correctly installed or vice versa based on the values A _DS , A _US which depend only on the attenuation of the communication line 13. However, if step 73 detects that the loop length l is available or can be determined, the detection of the reverse splitter 34 is also based on the loop length l. For this purpose, step 89 is performed to determine the loop length l. The loop length l can be determined by any suitable method. For example, the loop length l may be estimated by a SELT or MELT measurement procedure or by searching a loop length database that may be maintained by the network 11 operator.

Step 91 of block 63 calculates the threshold TH _DS (l) for the downstream direction and the threshold TH _US (l) for the upstream direction by analyzing the simulation results obtained in step 69. The threshold TH _DS (l) depends on the loop length l. FIG. 9 shows the calculation of this threshold TH _DS (l) in the downstream direction for the same exemplary scenario as FIG. Therefore, the simulation result represented by the attenuation curve (dotted line, broken line, solid line) corresponds to the simulation result shown in FIG. However, the threshold TH _DS (l) is a function of the loop length l. In the illustrated embodiment, the threshold TH _DS (l) is greater than the highest attenuation value A _DS (l) for any cable type and less than the lowest attenuation value A _DS (l) for any cable type. To be determined. This determination of the threshold is performed for each possible loop length l in order to obtain a loop length dependent threshold TH _DS (l). In particular, the threshold TH _DS (l) may be calculated so that it is at least essentially between the minimum and maximum attenuation values indicated by the dotted line in FIG. In the illustrated embodiment, step 91 calculates the loop length dependent threshold TH _DS (l) separately for the downstream and upstream directions, and thus the two loop length dependent thresholds TH _DS (l), TH _US ( l).

After step 91 has calculated the thresholds TH _DS (l), TH _US (l), branch 93 determines that both the measured attenuations A _DS , A _US have their respective thresholds for the loop length l determined in step 89. It is checked whether TH _DS (l) and TH _US (l) are exceeded. If so (Y), step 81 is performed to detect the reverse splitter 34. If not (N), yet another branch 94 checks whether both the measured attenuations A _DS , A _US are below the respective thresholds TH _DS (l), TH _US (l). If so (Y), step 85 is performed to determine if the splitter 34 is connected correctly or if the modem 19 is connected directly to the line 13 without using the splitter 34. The If not (N), a definitive conclusion as to whether the reverse splitter 34 exists is not possible and step 87 is performed.

The illustrated embodiment relies on loop length dependent thresholds TH _DS (l), TH _US (l) calculated for both upstream and downstream directions, but in different embodiments, the downstream or upstream direction Is only considered.

FIG. 10 shows block 65 in more detail. Block 65 may be executed when the modem 19 is not synchronized with the access node 17. In this case, the loop attenuation A _DS , A _US cannot be obtained. Accordingly, at least one different value depending on the attenuation of the communication line 13, for example the received signal power P of the at least one activation tone 55 a, 55 b, 55 c received by the first modem circuit 23 of the access node 17 is the splitter 34. Is used to determine whether is properly connected to the modem 19 or vice versa. Step 93 of block 65 simulates the received power P at the first modem circuit 23 of the access node 17 for each activation tone, for all possible cable types, and for the entire possible loop length range. To do. The simulation is performed for both direct transmission over the communication line 13 from at least one further communication line 36 to the communication line 13 and crosstalk of the activation tone. As described above with respect to step 69, the possible cable type and possible loop length range pairs may cover all possible networks 11 or some network operator's network 11 or some geographic It may be determined to cover the network 11 existing in the area. As in step 69, a mathematical cable model, such as the standard transmission line model described above, can be applied to perform the simulation. Crosstalk from yet another line 36 can be simulated using the FEXT model described below.

  FIG. 11 shows the simulation result generated by step 93. For simplicity, only one cable type is shown in FIG. Curves of received power level P associated with tone 9, tone 17, and tone 25 are labeled with reference numerals 55a, 55b, and 55c, respectively. The solid line corresponds to the case where the splitter 34 is correctly connected, and the dotted and dashed lines relate to the case where the splitter 34 is reversed. The broken line relates to a case where a reception signal is generated from another communication line 36 due to crosstalk. The simulation results shown in FIG. 11 are based on the assumption that modem 19 sends activation tones 55a, 55b, 55c at the maximum power allowed by the DSL standard of 38 dBm / Hz. The power level P of a fairly long line 13 with the splitter 34 correctly installed can be less than or equal to the power level P of the short line 13 in the reverse splitter 34, so the received power is between about -70 and about -90 dBm / Hz. It can be seen that it is impossible to reliably determine whether the splitter 34 is correctly connected or vice versa. Also, the activation tone received from the long line 13 at the reverse splitter 34 is not distinguishable from the activation tone received via crosstalk from another communication line 36 by using only a single threshold. Is possible.

  Step 95 of block 65 determines the received power level P at the access node 17 for each activation tone 55a, 55b, 55c. To this end, in one embodiment, the SELT is implemented while quiet line noise (quiet line noise: QLN) is measured while the modem 19 is transmitting activation tones 55a, 55b, 55c. Can be done. As a result, the measured QLN includes the signal power of the activation tone received at the access node 17. During the measurement of QLN, activation tones 55a, 55b, 55c sent by modem 19 can be detected and their power level P can be measured.

  A branch 97 is then executed to see if activation tones 55a, 55b, 55c are being received via crosstalk from yet another line 36. For this purpose, the crosstalk threshold THXT is preferably calculated according to the simulation result generated in step 93. In one embodiment, the crosstalk threshold THXT is selected as the maximum received power of the corresponding activation tone 55a, 55b, 55c received via crosstalk, ie, the maximum of the dashed line shown in FIG. The In FIG. 11, the crosstalk threshold THXT is shown for the activation tone 9 (dashed curve 55a). The crosstalk threshold THXT is thus calculated for the other activation tones 17 and 25 (dashed curves 55b and 55c). Branch 97 determines whether the received power level of all three activation tones is below their corresponding crosstalk threshold THXT and the received power P increases with the activation tone index, ie with the frequency of the activation tone. Check. If so (Y), block 65 detects in step 99 that a tone is received from another line 36 via crosstalk. If not (N), the splitter 34 may be reversed and another branch 101 is executed.

By using the 99% worst far-end crosstalk (FEXT) model found in standard ANSI T1.417, the crosstalk from yet another line 36 to the communication line 13 can be modeled, particularly simulated. According to this model, crosstalk can be described according to the following crosstalk transfer function:
F (f) = 10 · log ₁₀ (7.74 · 10 ²¹ · Ndist ^0.6 · Lcoup · f ² ) + Hlog (f) (1)

In the above equation, Ndist represents the number of disturbances (the number of further lines 36) that causes disturbance. Lcoup represents the coupling length, and Hlog represents the transfer function of the line 13 between the interfering transmitter insertion point and the access node 17. Assuming that there is only one thing causing the disturbance, the crosstalk transfer function F (f) depends on the frequency, the cable type (according to Hlog) and the coupling length Lcoup. The dependence on Lcoup is not monotonous. In fact, on the other hand, the transfer function increases with the bond length Lcoup by the term 10 · log ₁₀ (Lcoup). That is, the longer the coupling length, the more energy is transmitted via crosstalk. However, on the other hand, the crosstalk transfer function F (f) decreases with the coupling length by the term Hlog (f) (the signal transmitted farther is attenuated). Thus, for a given tone, there will be a coupling length that maximizes the crosstalk transfer function. This maximum value of the crosstalk transfer function is considered the “worst” coupling length that can be used in the simulation performed in step 93 in the illustrated embodiment. The crosstalk transfer function F (f) increases with the square of the frequency f as seen in equation (1), but the attenuation of the tones combined by the crosstalk only increases with the square root of the frequency, ie the tone index. . Accordingly, the power level of the activated tones 55a, 55b, 55c received from the further communication line 36 via crosstalk increases with frequency, ie the tone index. Thus, the criteria followed as the received signal power increases with the tone index can be used to determine whether the activated tones 55a, 55b, 55c are received by crosstalk.

  Branch 101 determines whether loop length l is available or required. If the branch 101 concludes that the loop length l is not available and cannot be determined (N), step 103 is executed. In step 103, the normal threshold value THAN and the reverse threshold value THAR are calculated from the simulation result obtained in step 93. The thresholds THAN and THAR are calculated separately for the activation tones 55a, 55b, 55c, respectively. In FIG. 11, exemplary values for these thresholds THAN, THAR are shown for an activated tone 55a having a tone index of 9.

  The normal splitter threshold THAN can be calculated as the maximum possible received power P for any possible cable type and any possible loop length, assuming that the splitter 34 is reversed. The reverse splitter threshold THAR may be calculated as the minimum possible received power P for any possible cable type and any possible loop length, assuming that the splitter 34 is correctly connected.

  The branch 105 of block 65 then determines whether at least two activation tones 55a, 55b, 55c have a power level P below their corresponding inverse threshold THAR. If so (Y), the reverse splitter is detected in step 107.

If not (N), branch 109 is executed to determine if there is an inverted splitter 34 in response to the received power level difference Δ between successive activated tones. In the illustrated embodiment, the minimum difference in received power between activation tones 9 and 17 for the reverse splitter 34 can be determined. In Figure 11, it is denoted by delta _R for this minimum difference. Also, assuming that the splitter 34 is correctly connected, the maximum difference in received power between the same activated tones with indices 9 and 17 can be calculated. In Figure 11 are denoted by the delta _N This maximum difference.

In one embodiment, the minimum difference delta _R is used as the first signal power difference threshold delta _R, the maximum difference delta _N is used as the second signal power difference threshold delta _N. The measured actual difference Δ in the received power P can be compared to these two signal power difference thresholds Δ _R , Δ _N. This comparison allows detection of the rate at which the signal power decreases with the frequency of the activation tone. If the measured difference delta is less than delta _N, the splitter 34 are properly connected (or splitter no) can be envisaged. If the measured difference delta is greater than delta _R, reverse splitter 34 can be detected. In one embodiment, therefore, this test is performed for sequence tones 17 and 25 in addition to or instead of the test for tones 9 and 17.

If at least one tone has a received signal power level P that exceeds the corresponding normal threshold THAN, in one embodiment, a correctly connected splitter 34 (or no splitter) may be assumed. However, if an activation tone is not received at a signal power level that exceeds the corresponding normal threshold THAN, then the measured difference Δ of subsequent activation tones is the threshold Δ _R calculated for a particular two activation tones, Additional testing based on comparing the delta _N may be implemented.

Thus, branch 109, the threshold Thar, is intended to link the test and based on the test signal power difference threshold delta _R delta _N based on THAN, activation tones with a signal power level P greater than the corresponding normal threshold THAN is And whether the measured threshold Δ exceeds the threshold Δ _R for each pair of subsequent activation tones (9, 17), (17, 25), ie Δ _R <Δ. If both conditions confirmed at branch 109 are true (Y), step 107 is performed to detect the reverse splitter 34. If it is not (N), it is possible to further another branch 110, measured signal power difference delta To verify that below the threshold delta _N. If so (Y), a correctly installed splitter 34 (or no splitter) is detected in step 111. If not (N), step 112 is performed to indicate that no conclusion can be made. In another embodiment, branch 109 considers only one pair (9,17) or (17,25) of subsequent activation tones.

  If the branch 101 determines that the loop length l is available or can be determined (Y), step 112 determines the loop length, for example, in the same manner as step 89, and step 113 is performed in step 93. From the simulation results, a single loop length-dependent threshold THA (l) is calculated for each of the activation tones 55a, 55b, and 55c. In FIG. 12, this loop length dependent threshold THA (l) is shown for an activation tone 55a having an index of 9. In one embodiment, threshold THA (l) is calculated for all activation tones 55a, 55b, 55c, whereby multiple values of threshold THA (l) are obtained for different activation tones.

  In one embodiment, assuming that the splitter is reversed, the threshold THA (l) corresponds to the maximum possible received power P for any cable type at that loop length l, separately for each loop length. Can be selected by level.

  Then, depending on the threshold THA (l), a branch 115 is performed to check whether at least two activation tones 55a, 55b, 55c have a received signal power level P below their corresponding loop length. If so (Y), step 107 is performed to detect the reversed splitter 34. If not (N), step 111 is performed to detect the correctly connected splitter 34 (or no splitter). After step 107 or step 111, block 65 is terminated.

  By using a loop length that depends on the threshold THA (l), accurate detection of the reverse splitter 34 is achieved even if the activation tones 55a, 55b, 55c are not being transmitted at full power by the modem 19. Is possible. If step 93 performs a simulation assuming the maximum allowable power according to the DSL standard, i.e. -38 dBm / Hz, and modem 19 sends an activation tone with less transmit power, the thresholds THAR, THAN, THAR (l) are probably high. Too much value. However, when the loop length dependent threshold THA (l) is used, there is a margin of about 20 dB between the threshold THA (l) and the curve (solid line) representing the received power at the complete transmission power. Thus, even if the modem 19 reduces its transmit power, the reverse splitter 34 detection is still accurate. If the received power level is below the crosstalk threshold THXT, a check on the received power vs. frequency, i.e. the activated tone index, must be made to ensure that the received tone does not come from yet another communication line 36. Don't be.

  In summary, each embodiment described herein allows detecting whether the splitter 34 of the CPE 21 is properly connected or reversed. The method 57 compares a value dependent on the attenuation of the communication line 13 with at least one threshold value. If information about the length of the communication line 13 (loop length) is available, a threshold dependent on the loop length can be calculated and compared with a value dependent on attenuation. If not, a fixed threshold can be calculated. When using a fixed threshold, two thresholds can be used to identify when a deterministic determination of whether the splitter 34 is properly connected cannot be made.

Depending on whether the modem 19 and the access node 17 are synchronized with each other, the value depending on the attenuation of the line 13 is a downstream and / or upstream loop measured when the modem 19 and the access node 17 are synchronized with each other. Attenuation A _DS , A _US , or received signal power level P at access node 17 when modem 19 and access node 17 are not synchronized with each other. This method 57 is performed by a monitoring station 39 that can communicate with these network elements 17, 19 using a suitable communication protocol via the network elements 17, 19 connected to the line 13 or the interconnection network 41. Can be executed. Thus, the method 57 can be performed, for example, by a network operator without requiring direct access to the CPE 21. Thus, the reverse splitter 34, usually caused by a customer error when installing the modem 19 or splitter 34, can be diagnosed easily and cost-effectively.

Claims (14)

A computer-implemented method (57) for inspecting customer premises equipment (21) comprising a DSL modem (19) coupled to a communication line (13), comprising:
At least one value (A _DS ) depending on the attenuation of the signal transmitted to the DSL modem (19) via the communication line (13) or received from the DSL modem (19) via the communication line (13). , A _US ; P) (71, 95);
The DSL modem (19) connects to a connector (52) on the DSL splitter (34) that is different from the modem connector (49) intended to be connected to the DSL modem (19) on the DSL splitter (34). In the manner of detecting that the DSL modem (19) is coupled to the communication line (13) via the DSL splitter (34) according to the values (A _DS , A _US ; P) ( 77, 93; 105, 109, 115),
Obtaining a loop length value (l) of the communication line (13);
A step (91; 113) of determining a threshold value (TH _DS (l), TH _US (l); THA (l)) according to the loop length value (l), and a detecting step (93; 115) Is based on comparing (93, 94, 115) a threshold (TH _DS (l), TH _US (l); THA (l)) with a value (A _DS , A _US ; P) Step (91; 113).   Conclude that the DSL modem (19) is correctly connected to the line (13) (85, 111), conclude that the DSL modem (19) is connected to a different connector (52) of the DSL splitter (34). Step (81, 107) and / or conclude that a definitive determination of whether the DSL modem (19) is correctly connected or connected to another connector (52) is impossible ( 87, 112). The method (57) of claim 1, comprising: The concluding step depends on comparing the values (A _DS , A _US ; P) with a first threshold (TN _DS , TN _US ; THAN) and a second threshold (TR _DS , TR _US ; THAR), The method (57) of claim 2. Method (57) according to any one of claims 1 to 3, wherein the value corresponds to a loop attenuation (A _DS , A _US ) of the communication line (13). A method (57) for inspecting customer premises equipment (21) comprising a DSL modem (19) coupled to a communication line (13),
At least one value (A _DS ) depending on the attenuation of the signal transmitted to the DSL modem (19) via the communication line (13) or received from the DSL modem (19) via the communication line (13). , A _US ; P) (71, 95);
The DSL modem (19) connects to a connector (52) on the DSL splitter (34) that is different from the modem connector (49) intended to be connected to the DSL modem (19) on the DSL splitter (34). In the manner of detecting that the DSL modem (19) is coupled to the communication line (13) via the DSL splitter (34) according to the values (A _DS , A _US ; P) ( 77, 93; 105, 109, 115),
The value corresponds to the received signal power (P) of the signal including at least one activation tone (55a, 55b, 55c), and at least one activation tone (55a, 55b, 55c) is connected to the communication line (13). Sent by the DSL modem (19) via the method (57).   Method (57) according to claim 5, comprising determining a value (P) for at least two different frequencies (55a, 55b, 55c) of the signal.   Checking (109) whether the rate at which the signal power (P) decreases with the frequency (f) of the signals (55a, 55b, 55c) is greater than a predefined speed threshold; and checking (109) ) Concludes that the DSL modem (19) is connected to yet another connector (52) if the speed indicates that it is greater than the speed threshold. Method (57).   The step (97) of checking whether the signal power increases with the frequency (f) of the signal (55a, 55b, 55c) and the step of checking (97) increases the signal power (P) with the frequency (f). And then concludes that the signal (55a, 55b, 55c) is the result of crosstalk from yet another communication line (13). (57). Whether the DSL modem (19) is connected to the modem connector (49) of the DSL splitter (34), including determining (61) whether the DSL modem (19) is synchronized with the access node (17 ) . Is based on the signal power (P) of the activation tone (55a, 55b, 55c) when the modem (19) is not synchronized, the conclusion step is when the modem (19) is synchronized. The method (57) according to any one of claims 1 to 8, which is based on a loop attenuation (A _DS , A _US ). A device (25, 31, 43) for inspecting a subscriber premises equipment (21) comprising a DSL modem (19) coupled to a communication line (13),
At least one value (A _DS ) depending on the attenuation of the signal transmitted to the DSL modem (19) via the communication line (13) or received from the DSL modem (19) via the communication line (13). , A _US ; P) (71, 95);
The DSL modem (19) connects to a connector (52) on the DSL splitter (34) that is different from the modem connector (49) intended to be connected to the DSL modem (19) on the DSL splitter (34). In the manner described above, the step (77) of detecting that the DSL modem (19) is coupled to the communication line (13) via the DSL splitter (34) according to the value (ADS, AUS; P). 93; 105, 109, 115),
Obtaining a loop length value (l) of the communication line (13);
A step (91; 113) of determining a threshold value (TH _DS (l), TH _US (l); THA (l)) according to the loop length value (l), and a detecting step (93; 115) Is based on comparing (93, 94, 115) a threshold (TH _DS (l), TH _US (l); THA (l)) with a value (A _DS , A _US ; P) Apparatus (25, 31, 43) configured to perform step (91; 113). A device (25, 31, 43) for inspecting a subscriber premises equipment (21) comprising a DSL modem (19) coupled to a communication line (13),
At least one value (A _DS ) depending on the attenuation of the signal transmitted to the DSL modem (19) via the communication line (13) or received from the DSL modem (19) via the communication line (13). , A _US ; P) (71, 95);
The DSL modem (19) connects to a connector (52) on the DSL splitter (34) that is different from the modem connector (49) intended to be connected to the DSL modem (19) on the DSL splitter (34). A step (77,) according to the value (ADS, AUS; P) that the DSL modem (19) is coupled to the communication line (13) via the DSL splitter (34). It is configured to perform 105,109,115) and; 93
The value corresponds to the received signal power (P) of the signal including at least one activation tone (55a, 55b, 55c), and at least one activation tone (55a, 55b, 55c) is connected to the communication line (13). Device (25, 31, 43) sent by the DSL modem (19) via 請 Motomeko is configured to perform a method (57) according to any one of 1 to 9, according to claim 10 or 11 (25,31,43).   A monitoring node (39) comprising a communication interface for connecting the monitoring node (39) to a network (11) comprising a subscriber premises equipment (21) comprising a DSL modem (19), comprising: A monitoring node (39) comprising the device (25, 31, 43) according to any one of the above. Computer (25,31,43) is programmed to perform the method (57) according to any one of claims 1 to 9 when operating in the computer program.

Images